Art of manufacturing curved printing plates



June 1 1926. 1,587,232

H. G. HOFF ART OF MANUFACTURING CURVED PRINTINGPLATES Filed Sept. 11, 1925 2 Shee t 1 June 1 1926.

H. G. HOFF ART OF MANUFACTURING CURVED PRINTING PLATES 2 Sheets-sheaf 2 @W6% if Patented June 1, 1926.

warren sates PATENT FFICE.

HARRY G. HOFF, OF CHICAGO, ILLINOIS, ASSIGNOR TO CHICAGO ELEOTROTYEE AND STEREOTYPE COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AIR/1 OF MANUFACTURING OURVED PRINTING PLATES.

Application filed September 11, 1925.. Serial No. 55,730.

This invention. relates to improvements in the art of manufacturing curved printing plates, and more especially to the manufacture of such curved printing plates as used on rotary presses, as, for example, electroplatcs comprising a sheet of metal, usually copper or nickel, and presenting the printing face, and having a relatively thick baching of metal, as, for example, what is known as electrotype backing metal.

in the manufacture of such curved plates, 7

the plate first produced in fiat form with the printing face formed thereon. Thereai'ter, the plate is bent to the desired curvature. My invention relates more particu larly to the method 0i and apparatus for so bending these plates.

In the bending of such plates, it is desirable to eliminate as far as possible stretching or other distortion of the printing face on the convex, or outer, surface of the plate. Such stretching causes a non-uniform distortion of the printing portions of the face with the result that accuracy in printing From the plate is impaired. This inaccuracy is always more or less objectionable and particularly so when the plate is adapted for inulti-color print-in In such case it is necessary that the contours of the printing portions of the successive plates used bear substantially accurate predetermined positions relative to each other in order that the accurate superposing of the inks of different colors, over the desired areas may be effect ed. Heretofore, the bending of such plates has been accomplished by heating the electrotype backing metalto soften it, in order to lessen such stretching or distortion of the printing face during the bending operation. Such heating of the backing metal, however,

takes some time and requires more or lesscon'iplicated apparatus.

In the bending of such printing plates Wl'lllE cold in accordance with the methods heretofore employed, such as, for example, by the use of rollers, the sheet bearing the printing surface is caused. to stretch, in the bending operation,'to such an extent as to relatively greatly distort the printing portions of the plate due to the combined thickness of the plate and backing, it being understood t-hat the sheet, and consequently the printing portions thereof, distort non-uniformly due to the irregular and non-uniform contours of the p n ng p i n all sh ets drically curved bed 11. vided at one end with a pinion wheel 16 having printing portions of dififerent contours distorting differently.

The primary object of my invention is to bend such printing plates to the desired curvature while cold, and without substantially stretching or distorting the printing face thereof.

In that form of device embodying the features of my invention shown in the accompanying drawings Figure 1 is a. view in side elevation of a bending machine showing a part broken away, Figure 2 is a similar view in top plan, Figure 3 is a view in end elevation, Figure -l' is a vertical sectional view showing the machine in operation, Figure 5 is a view taken as indicated by the line 5 on Fig. 2, and Figure 6 is an enlarged view of one end of the knife forming a part of the machine.

As shown in the drawings, 10 indicates a suitable base or support carrying the concavely curved'bed or trough 11. 12, 12 indicate strengthening ribs for the bed 11. It will be seen that the bed or trough 11, because of its curvature, is substantially in the shape of the lower half of a hollow cylinder.

At each end thebed 11 is provided with three radial Etl111S..-l3 carrying a bearing 14. in which is rotatably mounted a shaft 15 axially arranged with respect to the cylin The shaft 15 is proadapted to be operated by the worm 17 which is in turn adapted to be driven by the belt-wheel 18 actuated from any suitable source of power.

Rotatably mounted thereon, at each end, the shaft 15 carries a. collar 19. I Each of the collars 19 is provided with an upwardly projecting arm 20 and these two arms are connected by the operating bar 21. Each oi the collars 19 also carries a downwardly projecting shorter arm 22 the same being connected by the presser bar 23; The presser bar 23 extends substantially the length of the bed 11 and lies very close thereto. Movement of the operating bar 21 causes the presser bar to describe an are close to and adjacent the upper surface of the bed 11.

242 indicates a stop bar mounted on one edge of the trough or bed 11 having one edge 2% projecting inwardly a short distance beyond the curved surface of'such bed or trough. I

he sha 15 a a use pp 'press the block 32 out .1; 3 through suitable slot 25) in the knife to pe 111i; adjustment of said knife on said knife support. The knife 27 is provided with a plurality of stop screws on its upper edge adapted to be screwed out until their hen-ts engage the shalt 1e and thus furnish additional security to prevent undesired sliding niovenient oi the knife on the knife suoiort toward the shatt.

l l The limits suoiort carries at eacu end a roller supporting member 3i. Each oi the members Si carries l each carrvinrr rotatablv n'iounted therein .1 .1: 1'\ A 1',"

one one Oi a io iei dc). \jnp in u. on Kn on each side of the knife 24. Each 01 the roller bearing blocks 32 is adapted tor sliding movement in the ineinoer 3 substantiallv in a radial direction vi res to the :ixis of the shaft 15. This is accomplished by providing the guides or slides in which the blocks 82 are mounted. Each block 'arries a pin or holt project beyond the slide 32 and provided head 36 to hold the block 32 in the slide. :37 indicate a spira in the slide ing with a L spring arr nged \YlLll- UT: round the pin 35 tending to wardly, that is, away 5. It is to he understood roller bearing blocks 32- troin the shaft 4 i that each of the is supported it the same manner, so that the two rollers 33, 33, are yiel ily pressed toward the bed ll by the spring n a H1. l. L c 1 oo, oo nnicaie a iiut-ing p uLL in place in the bending machine, 2-38 indicating a sheet of metal forming the printing taco,

and 38 the son'iewhat thicker, sorter necking made 0? electrotype backing metal.

in the operation of the device, a print- Gill ing; plate placed in the machine with its upper edge against the stop bar and its lower edge against the presser bar 2.). the (.ipcratrng handle 21 is then lllOYQCl nianuah l to swing the prcsser tion toward the stop bar 2%", the plate until it con terms to t 1 (it the bed ll. At this point in the description of the opeiu-ition it should he note-rt that although the plate is thus l: o t e same curvature I it the bed ll, it i d no retain such ciiirvature upon release ot the press-er bar 48 but would spring; back somewhat. 'lhat is, there a CQl lilij l amount of elasticity in the plate which will cause it to spring back to a certain excnt it the presse'r bar 28 should be released before performing an other operation. In the use of the nachine, however, the plate is bent by means of the presser bar 23 as above described and then held in this position while the shaft 15' is caused to make one rotation.

wo bearing blocks The knife 27 having been priwiously justed to the correct position, the Jft 15 is caused to rotate whereupon the knife 2? shaves from the upper surn-tce oi? the backing a thin piece of the electrotvpe hacking metal as indicated by 38" in Fig. l. The rollers 3 83, are adjusted so that the springs 33' will press them down tightly against the plate during the shaving operatiou, it hein noted that one of the rollers is just in advance of the knife and the other just behind it. These rollers serve to hold and press the plate tightly against the hcd ll just in front. and just back oi? the cutting: zone. The shaving taken o'tl ot the hack of the plate the knife 27 is quite thin and otl sulis ci'uiu; tantiall in one large, tlat. sheet rt the lCPl'lQ is properly ad ust id and Alli-31 the plate has been shaved a; above described, the presscr bar 23, which uu' v be inanull v held in position during the ieration, is rel used, and the plate sh arp enough.

is stated above, the printing plate las a certain amount of elasticity or rcsi ienc so that being out cold, and then released, it will spring back to a certain e:-;tent tow? d its original shape. I have found, however, that it the plate is bent cold and then shaved on the back side as above dcstribcd, it will not spring back as as it the shaving operation has not been pertornied. in the practice of my invention, too much bendii'ig' must not be given cold by means of the prt ser bar 2 3. 'l hat is, if the plate in this step of the operation bent or UtiiWOii tOi much, there will be a certain amount of objectioi'ialile stretching or detouniaion of the "face, that tire amount 11 or curvature tha t can be given one plate by t e practice of my invent on in using one i-r chinc, is limited The exact. amount of ciurature :Lt "ii to given by one machine and with orniation of the plate can he (lQULlllllllQtl c inentation. It will he on w, H. t. scan, noheici, unit an (lCJllOi (module may be given to late by the use (it two or more machine. which case, the plate is put through said inz'cluncs succe iveli. For exauttple, l have Found that one machine 3*;17 undo j ,rj V j! LO not o ion a gait not to what urvatu Anlit) original curvature. For example, if a machine is made to bend a plate from a number curvature to a number 1-5 curvature, the curvature of the bed 11 must be somewhat greater (that is, for a shorter radius) than a number curvature. In the use of such machine, the plate is first bent to a 55 curvature by other similar in chines. It is then placed in the machine in question and by means of the presser bar 23 caused to conform to the. curvature of the bed 11 which is, as stated, somewhat greater than a lo curvature. lhe shaving operation is then performed, and upon release of the plate from the machine, it will spriug'bach until it has a 45 curvature.

In general it may be that in carrying out my invention, the plate must not be bent too much by one n achine. If the plate is not bent by the pres. bar in any one machine, beyond the limit of its elasticity, all stretching and distortion will be substantially eliminated. In such case, the original bend given by the proper bar 333 not curving the plate beyond limit of elas-- ticity, will cause no distortion or stretching. The shaving operation carried on while the plate is held in this curvatuie will prevent it from going back to its original shape. It will he seen, therefore, that the machine will thus give the plate a certain amount of permanent curvature with no distortion or stretching. ()bviously the curvature may be increased by successive operations in differentmachines to any desired extent. In practice, I have found, however, that in any one machine the first bend or ourature given by the presser bar 23 may be somewhat beyond the limit of elasticity of the plate without causing any objectionable distortion or stretching. The exact amount of curvature given to the plate by any one machine may be as great as desired as long as there is no objectionable stretchinn; or distortion.

fs hilc I have illustrated auu described a particular construction embodying my in vention, I do not wish to be understood as intending to limit it thereto, as the same may be variously modified and altered without departing from the sp .lll and scope of the invention. V

What I claim as new, and desire to secure by Letters Patent, is:

1. The method of curving printing plates which consists in bending; the plate somewhat beyond the desired ultimate curvature and shaving a portion oil of the back thereof.

2. The method of curving printing plates which consists in bending the plate somewhat beyond the desired ultimate curvature and shaving a thin film oil of the back thereof.

3. The method of curving printing plates which consists in f rcing; the plate face down on a bed having a curvature somewhat greater than the desired ultimate curvature and shaving a portion oil of the back thereof while holding said plate in contact with said bed.

The method of curving printing plates which consists in forcing the plate face down on a bed having a curvature somewhat greater than the desired ultimate curvature and shaving a thin film of the back thereof.

5. The method of curving printing plates which consists in forcing the plate face down on to a bed having a. cur ature somewhat greater than the desired ultimate curvature and shaving a portion off 'of the back thereof while maintaining pressure upon said plate in advance of the shaving Zone to hold said plate in contact with said bed.

6. The method of curving printing plates which consists in forcing the plate face down on to a bed having a curvature somewhat greater than the desired ultimate curvature and shaving a portion off of the back thereof while maintaining pressure upon said plate in advance of and back of the shaving zone to hold said plate in contact with said bed.

7'. The method of curving printing plates which consists in forcing the plate face down on to a bed having a curvature some what greater than the desired ultimate curvature and shaving a thin film oft of the back thereof while maintaining pressure upon said plate in advance of the shaving zone to hold said plate in contact with said bed.

8. The method of curving printing plates which consists in forcing the plate face down on to a bed having a curvature somewhat greater than the desired ultimate curvature and shaving a thin lihn elf of the back thereof while maint-aining;- pressure upon said plate in advance of and back of the shaving @one to hold said plate in contact with salt ill) geptember, l9

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